import numpy as np
import cv2 as cv
def nothing(x):
    pass
# Create a black image, a window
img =np.zeros((300,512,3),np.uint8)
cv.namedWindow('image')
# create trackbars for color change
cv.createTrackbar('R','image',0,255,nothing)
cv.createTrackbar('G','image',0,255,nothing)
cv.createTrackbar('B','image',0,255,nothing)

switch='0 : OFF \n1 : ON'
cv.createTrackbar(switch,'image',0,1,nothing)

while(1):
  cv.imshow('image',img)
  k= cv.waitKey(1) & 0xFF
  if k == 27:
     break
  r= cv.getTrackbarPos('R','image')
  g= cv.getTrackbarPos('G','image')
  b= cv.getTrackbarPos('B','image')
  s= cv.getTrackbarPos(switch,'image')
  if s == 0:
    img[:]= 0
  else:
    img[:] = [b,g,r]
cv.destroyAllWindows()